A copending invention disclosure, "Group-Complementary Code Sets for Implementing Pulse-Compression Processing with Optimized Aperiodic Autocorrelation and Optimized Cross-Correlation Properties" Ser. No. 362,934, described a waveform structure, called group-complementary codes, which occurs in orthogonal groups and provides zero temporal sidelobes over the pulse repetition interval. This invention disclosure describes a different correlator and waveform structure that is an extension of the group-complementary coding technique, and which not only provides the optimized autocorrelation properties of group-complementary codes but also allows optimization of the spectral-sidelobe response in the frequency domain.
Group-complementary coding is a process that utilizes the individual responses of K pulses in an active sensor system to form a composite response, with the property that the autocorrelation function will have zero temporal sidelobes over the pulse unambiguous interval. In forming the composite response, the responses of the individual pulses are algebraically added, with the same weight given to each pulse. In many sensor applications, filter formation for the purpose of spectral analysis follows a pulse-compression processor. In such applications, a number of pulse responses are processed as a group of operands, in an algorithm such as the Discrete Fourier Transform. It is feasible to combine multipulse summation and spectral (filter formation) processing (with the uniform weight-per-pulse response required for temporal sidelobe cancellation). However, uniform weighting results in relatively large sidelobes in the spectral domain. This invention disclosure describes a technique that will allow group-complementary-type processing for temporal sidelobe cancellation and still permit weighting of the pulse responses to reduce or minimize frequency domain sidelobes. The technique, then, allows optimization in both dimensions of the receiver ambiguity response. Whenever weighting is applied to control spectral sidelobes, some mismatch loss occurs as an unavoidable penalty. Further, this loss appears to increase slightly whenever the temporal sidelobe control is accommodated. The cost of this optimization is in the filter mismatch loss that will, in general, be present because of weighting applied to individual pulse responses.